<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script src="https://cdn.jsdelivr.net/npm/vue@2.6.10/dist/vue.js"></script>
</head>

<body>
    <div id="app">
        <h1>全名:{{fullName}}</h1>
      </div>
      <script>
        Vue.config.productionTip = false;
        //   使用watch来书写获取全名的逻辑,感受watch和computed的区别
        const vm = new Vue({
          el: "#app",
          data() {
            return {
              firstName: "wang",
              lastName: "zhongwang",
              fullName: "",
            };
          },
          watch: {
            firstName: {
              immediate: true,
              handler() {
                this.fullName =this.firstName.toLowerCase() +" " +this.lastName.toLowerCase();
              },
            },
            lastName: {
              immediate: true,
              handler() {
                this.fullName =this.firstName.toLowerCase() +" " +this.lastName.toLowerCase();
              },
            },
          },
        });
      </script>
</body>

</html>